You may play well or you may play badly; the important thing is that you should play truly,’ wrote Shchepkin to his pupil Shumski. To play truly means to be right, logical, coherent, to think, strive, feel and act in unison with your role.
If you take all these internal processes, and adapt them to the spiritual and physical life of the person you are representing, we call that living the part. This is of supreme significance in creative work. Aside from the fact that it opens up avenues for inspiration, living the part helps the artist to carry out one of his main objectives. His job is not to present merely the external life of his character. He must fit his own human qualities to the life of this other person, and pour into it all of his own soul. The fundamental aim of our art is the creation of this inner life of a human spirit, and its expression in an artistic form.
That is why we begin by thinking about the inner side of a role, and how to create its spiritual life through the help of the internal process of living the part. You must live it by actually experiencing feelings that are analogous to it, each and very time you repeat the process of creating it.
— Constantin Stanislavski, An Actor Prepares, 1936